"This is the definition of overthinking, dear. Don't question how or why--just do for a little while. It's simply a matter of existence, which is what you are capable of no matter what--you don't have to do it particularly well, you just have to do it at all. (Not a euphemism, unfortunately.)"
"See? Things can be okay if you stop, um, thinking about them--even the perspectives, the at leasts, the maybes and what ifs, the possibilities and concentrate on the right now, the breath in, the guffaw out, the pointless revelations, the fruitless debates, the this very second moments of life--those tend to be bearable. It's everything else that sucks the life right out of you, erases the pleasant visage that doesn't come easily anyway, makes every breath in a conscious effort, every breath out an involuntary sigh."
"Oscillate between moments of normalcy and the lingering catastrophic self-doubt. I mean, this is what people DO to me, you know? I can't change it; I just have to surround myself with people who bring out the best in me. Well, obviously. Also, I must figure out what I want, although I have figured out why cannot: everything I've truly desired, worked for, and received, has been taken away from me for reasons beyond my control (boarding school being the prevalent example). What to do about that, then?"
And in the meantime, work! Go in early! Stay late! Find that point of exhaustion so you can get to sleep! Go on walks to discover the baskets full of puppies, the meadows full of bunnies, the parks full of bats, the random bits of life that exhilarate and surprise you. And when you are ready, regardless of whether you think you are or not, something good will happen that you'll never see coming and that's when it will all be worth it.